Buggy code:
public abstract class DataSourceUtils { public static final int CONNECTION_SYNCHRONIZATION_ORDER = 1000 ; private static final Log logger = LogFactory . getLog ( DataSourceUtils . class ) ; public static Connection getConnection ( DataSource dataSource ) throws CannotGetJdbcConnectionException { } public static Connection doGetConnection ( DataSource dataSource ) throws SQLException { } public static Integer prepareConnectionForTransaction ( Connection con , TransactionDefinition definition ) throws SQLException { Assert . notNull ( con , "No<seq2seq4repair_space>Connection<seq2seq4repair_space>specified" ) ; if ( ( definition != null ) && ( definition . isReadOnly ( ) ) ) { try { if ( DataSourceUtils . logger . isDebugEnabled ( ) ) { DataSourceUtils . logger . debug ( ( ( "Setting<seq2seq4repair_space>JDBC<seq2seq4repair_space>Connection<seq2seq4repair_space>[" + con ) + "]<seq2seq4repair_space>read-only" ) ) ; } con . setReadOnly ( true ) ; } catch ( Throwable ex ) { DataSourceUtils . logger . debug ( "Could<seq2seq4repair_space>not<seq2seq4repair_space>set<seq2seq4repair_space>JDBC<seq2seq4repair_space>Connection<seq2seq4repair_space>read-only" , ex ) ; } } Integer previousIsolationLevel = null ; if ( ( definition != null ) && ( ( definition . getIsolationLevel ( ) ) != ( TransactionDefinition . ISOLATION_DEFAULT ) ) ) { if ( DataSourceUtils . logger . isDebugEnabled ( ) ) { DataSourceUtils . logger . debug ( ( ( ( "Changing<seq2seq4repair_space>isolation<seq2seq4repair_space>level<seq2seq4repair_space>of<seq2seq4repair_space>JDBC<seq2seq4repair_space>Connection<seq2seq4repair_space>[" + con ) + "]<seq2seq4repair_space>to<seq2seq4repair_space>" ) + ( definition . getIsolationLevel ( ) ) ) ) ; } <START_BUG> previousIsolationLevel = new Integer ( con . getTransactionIsolation ( ) ) ; <END_BUG> con . setTransactionIsolation ( definition . getIsolationLevel ( ) ) ; } return previousIsolationLevel ; } public static void resetConnectionAfterTransaction ( Connection con , Integer previousIsolationLevel ) { } public static boolean isConnectionTransactional ( Connection con , DataSource dataSource ) { } public static void applyTransactionTimeout ( Statement stmt , DataSource dataSource ) throws SQLException { } public static void applyTimeout ( Statement stmt , DataSource dataSource , int timeout ) throws SQLException { } public static void releaseConnection ( Connection con , DataSource dataSource ) { } public static void doReleaseConnection ( Connection con , DataSource dataSource ) throws SQLException { } private static boolean connectionEquals ( ConnectionHolder conHolder , Connection passedInCon ) { } public static Connection getTargetConnection ( Connection con ) { } private static int getConnectionSynchronizationOrder ( DataSource dataSource ) { } private static class ConnectionSynchronization extends TransactionSynchronizationAdapter { private final ConnectionHolder connectionHolder ; private final DataSource dataSource ; private int order ; private boolean holderActive = true ; public ConnectionSynchronization ( ConnectionHolder connectionHolder , DataSource dataSource ) { } @ Override public int getOrder ( ) { } @ Override public void suspend ( ) { } @ Override public void resume ( ) { } @ Override public void beforeCompletion ( ) { } @ Override public void afterCompletion ( int status ) { } } }

Fix:
previousIsolationLevel = con . getTransactionIsolation ( ) ;